The invention relates to an automatic clutch control system which automatically controls the coupling of a driven shaft to a drive shaft in a clutch mounted on an automobile in accordance with a decision rendered by an electronic circuit.
In a conventional automatic clutch arrangement, to achieve an accurate engagement of a clutch without experiencing shock, there has been proposed a clutch arrangement in which a clutch transmits rotating power to an output shaft. The arrangement comprises a power sensor for detecting the number of revolutions of the output shaft, a clutch sensor for detecting the number of revolutions of the clutch, a comparator for determining the relative magnitude of the number of revolutions of both sensors, a parameter of follow-up control responsive to an output from the comparator to activate the clutch for engagement as the number of revolutions of the output shaft increases whenever the number of revolutions of the output shaft is higher than that of the clutch, and an automatic engaging circuit responsive to an output from the comparator and operating whenever the number of revolutions of the clutch is higher to deactuate the follow-up control and to terminate automatically the engagement of the clutch within a given time interval. In this manner, the relative magnitude of the number of revolutions of the engine and the clutch is determined in an electrical manner, and whenever the number of revolutions of the engine is higher than that of the clutch, an engagement of the clutch occurs in response to the number of revolutions of the engine while whenever the number of revolutions of the engine is lower than that of the clutch, an engagement of the clutch takes place in accordance with a difference therebetween. (See Japanese Patent Publication No. 26,020/1798, filed Mar. 26, 1971 and published July 31, 1978). In other words, the rotational speed of the engine is chosen as a main variable while a differential speed between the output shaft of the clutch (driven shaft) and the output shaft of the engine (the clutch drive shaft) is chosen as a parameter for controlling the clutch coupling power. To summarize, in a mode in which the vehicle is driven for running under the engine power, the clutch coupling power is controlled in a manner corresponding to the rotational speed of the engine, while, in an engine brake mode, the clutch coupling power is controlled as a particular function of time. Consequently, the slip rate of the clutch depends on the rotational speed of the engine, and the correlation between the engine power and a load on the vehicle may be be proper.
To achieve a proper engagement of a clutch for various running conditions of a vehicle, commonly assigned U.S. Pat. Nos. 4,518,068, 4,529,072 and 4,475,637 disclose a system for controlling the pressure with which a clutch is engaged, with a slip rate of the clutch, which is equal to the ratio of the rotational speed No of a driven shaft against the rotational speed Ne of a drive shaft, as a main parameter. The slip rate e corresponds to the rotational speed No and Ne of the driven shaft and the drive shaft respectively, therefore the clutch coupling power corresponds to running condition of the vehicle. A microprocessor of the system, in the first clutch control, initially applies to the clutch an engaging force of a reduced magnitude to detect the rate of change (dNe/dt) of the rotational speed Ne of the clutch drive shaft, which is utilized as indicative of the correlation between the loading and the engine power in determining a clutch turn-on response. Throttle opening is used to determine the engine power. The combination of the vehicle load and the engine power specifies a particular data group (Vsx=f(t)) having a proper clutch ON change rate (dVs/dt) in the first time segment l=0. The clutch controlling signal Vsx is changed at a time subinterval of .DELTA.T= 0.05 sec. In the segment l=0, ##EQU1## After proceeding through the segment l=0, the clutch ON control enters the second time segment l=1. During the clutch ON control for the second time l=1, the actual slip rate e is utilized as indicative of the vehicle load, and the throttle opening is utilized as indicative of the engine power in the same manner as in the first time segment. These specify a particular group of clutch controlling data Vsx=f(t) having a proper clutch ON change rate (dVs/dt) for the second segment l=1. The clutch control signal Vsx is changed at a time subinterval of .DELTA.t=tt sec. In the second segment l=1, ##EQU2## After proceeding through the time segment l=1, the clutch ON control in the third time segment l=2 is entered. This takes place in the similar manner as during the time segment l=1. A similar clutch ON control is repeated for the segments l=3, 4, . . . .
The aforesaid clutch control is executed by a microcomputer system having a center processing unit CPU (microprocessor or microcomputer), RAM and ROM. A program for executing the clutch control is stored in a ROM of CPU and/or an additional ROM. Also the data groups each of which will be specified by the throttle opening and the vehicle load dNe/dt as well as the data groups each of which will be specified by the throttle opening and the actual slip rate e=No/Ne are stored in the additional ROM. Each of the data groups includes 8 data which will be read out in order and have a specific change rate. Selection of a data group in turn and reading out of each data therein causes an increment of the clutch coupling power with a change rate which corresponds to the throttle opening as well as the vehicle load or the actual slip rate.
The clutch ON control in which the parameters including the throttle opening, the speed Ne and the speed No are read in and a clutch controlling data group is accessed by the parameters with a predetermined time segment period also each data of the data group is read out in succession with a short subinterval as described hereinbefore, may experience an abrupt acceleration or deceleration of the vehicle which may cause a shock to the vehicle and the driver by an abrupt change of the clutch control pressure due to a breakage of a continuity between a clutch control pressure indicated by the last data of a preceding data group and a clutch control pressure indicated by the first data of a subsequent data group. The breakage of the continuity may be experienced when a segmentation or a digitization is relatively rough to reduce a number of the data groups, when a change of the throttle opening is relatively first large or when a change of the vehicle load is relatively large due to a road condition.